The air secondary battery using a nonaqueous liquid electrolyte is a secondary battery using air (oxygen) as a cathode active material and has advantages including high energy density and easy reduction in size and weight. Therefore, currently, it has been attracting attention as a high-capacity secondary battery better than widely-used lithium secondary batteries.
The air secondary battery comprises: an air cathode layer having, for example, a conductive material (e.g., carbon black), a catalyst (e.g., manganese dioxide), and a binder (e.g., polyvinylidene fluoride), an air cathode current collector which collects current of the air cathode layer, an anode layer containing an anode active material (e.g., metal Li), an anode current collector which collects current of the anode layer, and a nonaqueous liquid electrolyte which conducts a metal ion (e.g., Li ion).
Conventionally, the air secondary battery which utilizes oxygen in the atmosphere has been known as a source of oxygen to be used at the time of discharge. Usually, the air secondary battery has an opening portion in a battery case. At the time of discharge, oxygen is supplied from the opening portion. At the time of charge, oxygen is evacuated from the opening portion. With reference to the air secondary battery focused on the evacuation of oxygen, for example, Patent Document 1 discloses the air secondary battery which has a gas discharge hole in the battery case and the hole discharges gas generated in the battery case. The technique prevents excessive carbon dioxide intake from the atmosphere and excessive water loss from the battery by devising such as the shape of the gas discharge hole.
On the other hand, an air battery in which a carboxymethyl cellulose-based polymer layer is provided between a cathode catalyst layer (air cathode layer) and the separator is disclosed in Patent Document 2. The technique involves the process of reducing the battery internal resistance by bonding the cathode catalyst layer and the separator with the carboxymethyl cellulose-based polymer layer. As an example of the conventional air cathode layers, a cathode (air cathode layer) which is based on a carbonaceous material in which the pore volume occupied by pores having a diameter of 1 nm or more is 1.0 ml/g or more is disclosed in Patent Document 3.    Patent Documents 1: Japanese translation of PCT International Application No. 9-500480    Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2007-157445    Patent Document 3: JP-A No. 2002-15737